0
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1 /*
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2 * Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 # include "incls/_precompiled.incl"
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26 # include "incls/_attachListener_linux.cpp.incl"
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27
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28 #include <unistd.h>
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29 #include <signal.h>
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30 #include <sys/types.h>
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31 #include <sys/socket.h>
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32 #include <sys/un.h>
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33 #include <sys/stat.h>
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34
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35 // The attach mechanism on Linux uses a UNIX domain socket. An attach listener
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36 // thread is created at startup or is created on-demand via a signal from
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37 // the client tool. The attach listener creates a socket and binds it to a file
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38 // in the filesystem. The attach listener then acts as a simple (single-
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39 // threaded) server - tt waits for a client to connect, reads the request,
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40 // executes it, and returns the response to the client via the socket
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41 // connection.
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42 //
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43 // As the socket is a UNIX domain socket it means that only clients on the
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44 // local machine can connect. In addition there are two other aspects to
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45 // the security:
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46 // 1. The well known file that the socket is bound to has permission 400
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47 // 2. When a client connect, the SO_PEERCRED socket option is used to
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48 // obtain the credentials of client. We check that the effective uid
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49 // of the client matches this process.
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50
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51 // forward reference
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52 class LinuxAttachOperation;
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53
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54 class LinuxAttachListener: AllStatic {
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55 private:
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56 // the path to which we bind the UNIX domain socket
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57 static char _path[PATH_MAX+1];
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58 static bool _has_path;
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59
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60 // the file descriptor for the listening socket
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61 static int _listener;
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62
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63 static void set_path(char* path) {
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64 if (path == NULL) {
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65 _has_path = false;
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66 } else {
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67 strncpy(_path, path, PATH_MAX);
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68 _path[PATH_MAX] = '\0';
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69 _has_path = true;
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70 }
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71 }
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72
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73 static void set_listener(int s) { _listener = s; }
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74
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75 // reads a request from the given connected socket
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76 static LinuxAttachOperation* read_request(int s);
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77
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78 public:
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79 enum {
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80 ATTACH_PROTOCOL_VER = 1 // protocol version
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81 };
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82 enum {
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83 ATTACH_ERROR_BADVERSION = 101 // error codes
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84 };
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85
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86 // initialize the listener, returns 0 if okay
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87 static int init();
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88
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89 static char* path() { return _path; }
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90 static bool has_path() { return _has_path; }
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91 static int listener() { return _listener; }
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92
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93 // write the given buffer to a socket
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94 static int write_fully(int s, char* buf, int len);
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95
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96 static LinuxAttachOperation* dequeue();
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97 };
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98
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99 class LinuxAttachOperation: public AttachOperation {
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100 private:
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101 // the connection to the client
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102 int _socket;
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103
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104 public:
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105 void complete(jint res, bufferedStream* st);
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106
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107 void set_socket(int s) { _socket = s; }
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108 int socket() const { return _socket; }
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109
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110 LinuxAttachOperation(char* name) : AttachOperation(name) {
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111 set_socket(-1);
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112 }
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113 };
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114
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115 // statics
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116 char LinuxAttachListener::_path[PATH_MAX+1];
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117 bool LinuxAttachListener::_has_path;
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118 int LinuxAttachListener::_listener = -1;
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119
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120 // Supporting class to help split a buffer into individual components
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121 class ArgumentIterator : public StackObj {
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122 private:
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123 char* _pos;
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124 char* _end;
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125 public:
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126 ArgumentIterator(char* arg_buffer, size_t arg_size) {
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127 _pos = arg_buffer;
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128 _end = _pos + arg_size - 1;
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129 }
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130 char* next() {
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131 if (*_pos == '\0') {
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132 return NULL;
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133 }
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134 char* res = _pos;
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135 char* next_pos = strchr(_pos, '\0');
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136 if (next_pos < _end) {
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137 next_pos++;
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138 }
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139 _pos = next_pos;
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140 return res;
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141 }
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142 };
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143
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144
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145 // atexit hook to stop listener and unlink the file that it is
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146 // bound too.
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147 extern "C" {
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148 static void listener_cleanup() {
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149 static int cleanup_done;
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150 if (!cleanup_done) {
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151 cleanup_done = 1;
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152 int s = LinuxAttachListener::listener();
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153 if (s != -1) {
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154 ::close(s);
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155 }
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156 if (LinuxAttachListener::has_path()) {
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157 ::unlink(LinuxAttachListener::path());
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158 }
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159 }
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160 }
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161 }
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162
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163 // Initialization - create a listener socket and bind it to a file
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164
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165 int LinuxAttachListener::init() {
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166 char path[PATH_MAX+1]; // socket file
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167 int listener; // listener socket (file descriptor)
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168
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169 // register function to cleanup
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170 ::atexit(listener_cleanup);
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171
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172 // create the listener socket
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173 listener = ::socket(PF_UNIX, SOCK_STREAM, 0);
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174 if (listener == -1) {
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175 return -1;
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176 }
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177
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178 int res = -1;
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179 struct sockaddr_un addr;
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180 addr.sun_family = AF_UNIX;
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181
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182 // FIXME: Prior to b39 the tool-side API expected to find the well
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183 // known file in the working directory. To allow this libjvm.so work with
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184 // a pre-b39 SDK we create it in the working directory if
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185 // +StartAttachListener is used is used. All unit tests for this feature
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186 // currently used this flag. Once b39 SDK has been promoted we can remove
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187 // this code.
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188 if (StartAttachListener) {
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189 sprintf(path, ".java_pid%d", os::current_process_id());
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190 strcpy(addr.sun_path, path);
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191 ::unlink(path);
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192 res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr));
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193 }
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194 if (res == -1) {
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195 sprintf(path, "%s/.java_pid%d", os::get_temp_directory(), os::current_process_id());
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196 strcpy(addr.sun_path, path);
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197 ::unlink(path);
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198 res = ::bind(listener, (struct sockaddr*)&addr, sizeof(addr));
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199 }
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200 if (res == -1) {
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201 RESTARTABLE(::close(listener), res);
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202 return -1;
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203 }
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204 set_path(path);
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205
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206 // put in listen mode and set permission
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207 if ((::listen(listener, 5) == -1) || (::chmod(path, S_IREAD|S_IWRITE) == -1)) {
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208 RESTARTABLE(::close(listener), res);
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209 ::unlink(path);
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210 set_path(NULL);
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211 return -1;
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212 }
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213 set_listener(listener);
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214
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215 return 0;
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216 }
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217
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218 // Given a socket that is connected to a peer we read the request and
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219 // create an AttachOperation. As the socket is blocking there is potential
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220 // for a denial-of-service if the peer does not response. However this happens
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221 // after the peer credentials have been checked and in the worst case it just
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222 // means that the attach listener thread is blocked.
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223 //
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224 LinuxAttachOperation* LinuxAttachListener::read_request(int s) {
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225 char ver_str[8];
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226 sprintf(ver_str, "%d", ATTACH_PROTOCOL_VER);
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227
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228 // The request is a sequence of strings so we first figure out the
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229 // expected count and the maximum possible length of the request.
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230 // The request is:
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231 // <ver>0<cmd>0<arg>0<arg>0<arg>0
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232 // where <ver> is the protocol version (1), <cmd> is the command
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233 // name ("load", "datadump", ...), and <arg> is an argument
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234 int expected_str_count = 2 + AttachOperation::arg_count_max;
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235 int max_len = (strlen(ver_str) + 1) + (AttachOperation::name_length_max + 1) +
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236 AttachOperation::arg_count_max*(AttachOperation::arg_length_max + 1);
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237
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238 char buf[max_len];
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239 int str_count = 0;
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240
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241 // Read until all (expected) strings have been read, the buffer is
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242 // full, or EOF.
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243
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244 int off = 0;
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245 int left = max_len;
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246
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247 do {
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248 int n;
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249 RESTARTABLE(read(s, buf+off, left), n);
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250 if (n == -1) {
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251 return NULL; // reset by peer or other error
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252 }
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253 if (n == 0) {
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254 break;
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255 }
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256 for (int i=0; i<n; i++) {
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257 if (buf[off+i] == 0) {
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258 // EOS found
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259 str_count++;
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260
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261 // The first string is <ver> so check it now to
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262 // check for protocol mis-match
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263 if (str_count == 1) {
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264 if ((strlen(buf) != strlen(ver_str)) ||
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265 (atoi(buf) != ATTACH_PROTOCOL_VER)) {
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266 char msg[32];
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267 sprintf(msg, "%d\n", ATTACH_ERROR_BADVERSION);
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268 write_fully(s, msg, strlen(msg));
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269 return NULL;
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270 }
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271 }
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272 }
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273 }
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274 off += n;
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275 left -= n;
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276 } while (left > 0 && str_count < expected_str_count);
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277
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278 if (str_count != expected_str_count) {
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279 return NULL; // incomplete request
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280 }
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281
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282 // parse request
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283
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284 ArgumentIterator args(buf, (max_len)-left);
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285
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286 // version already checked
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287 char* v = args.next();
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288
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289 char* name = args.next();
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290 if (name == NULL || strlen(name) > AttachOperation::name_length_max) {
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291 return NULL;
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292 }
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293
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294 LinuxAttachOperation* op = new LinuxAttachOperation(name);
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295
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296 for (int i=0; i<AttachOperation::arg_count_max; i++) {
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297 char* arg = args.next();
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298 if (arg == NULL) {
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299 op->set_arg(i, NULL);
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300 } else {
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301 if (strlen(arg) > AttachOperation::arg_length_max) {
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302 delete op;
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303 return NULL;
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304 }
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305 op->set_arg(i, arg);
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306 }
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307 }
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308
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309 op->set_socket(s);
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310 return op;
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311 }
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312
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313
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314 // Dequeue an operation
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315 //
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316 // In the Linux implementation there is only a single operation and clients
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317 // cannot queue commands (except at the socket level).
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318 //
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319 LinuxAttachOperation* LinuxAttachListener::dequeue() {
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320 for (;;) {
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321 int s;
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322
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323 // wait for client to connect
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324 struct sockaddr addr;
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325 socklen_t len = sizeof(addr);
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326 RESTARTABLE(::accept(listener(), &addr, &len), s);
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327 if (s == -1) {
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328 return NULL; // log a warning?
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329 }
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330
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331 // get the credentials of the peer and check the effective uid/guid
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332 // - check with jeff on this.
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333 struct ucred cred_info;
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334 socklen_t optlen = sizeof(cred_info);
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335 if (::getsockopt(s, SOL_SOCKET, SO_PEERCRED, (void*)&cred_info, &optlen) == -1) {
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336 int res;
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337 RESTARTABLE(::close(s), res);
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338 continue;
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339 }
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340 uid_t euid = geteuid();
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341 gid_t egid = getegid();
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342
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343 if (cred_info.uid != euid || cred_info.gid != egid) {
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344 int res;
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345 RESTARTABLE(::close(s), res);
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346 continue;
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347 }
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348
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349 // peer credential look okay so we read the request
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350 LinuxAttachOperation* op = read_request(s);
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351 if (op == NULL) {
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352 int res;
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353 RESTARTABLE(::close(s), res);
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354 continue;
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355 } else {
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356 return op;
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357 }
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358 }
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359 }
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360
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361 // write the given buffer to the socket
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362 int LinuxAttachListener::write_fully(int s, char* buf, int len) {
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363 do {
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364 int n = ::write(s, buf, len);
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365 if (n == -1) {
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366 if (errno != EINTR) return -1;
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367 } else {
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368 buf += n;
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369 len -= n;
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370 }
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371 }
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372 while (len > 0);
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373 return 0;
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374 }
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375
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376 // Complete an operation by sending the operation result and any result
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377 // output to the client. At this time the socket is in blocking mode so
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378 // potentially we can block if there is a lot of data and the client is
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379 // non-responsive. For most operations this is a non-issue because the
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380 // default send buffer is sufficient to buffer everything. In the future
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381 // if there are operations that involves a very big reply then it the
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382 // socket could be made non-blocking and a timeout could be used.
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383
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384 void LinuxAttachOperation::complete(jint result, bufferedStream* st) {
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385 JavaThread* thread = JavaThread::current();
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386 ThreadBlockInVM tbivm(thread);
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387
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388 thread->set_suspend_equivalent();
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389 // cleared by handle_special_suspend_equivalent_condition() or
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390 // java_suspend_self() via check_and_wait_while_suspended()
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391
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392 // write operation result
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393 char msg[32];
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394 sprintf(msg, "%d\n", result);
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395 int rc = LinuxAttachListener::write_fully(this->socket(), msg, strlen(msg));
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396
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397 // write any result data
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398 if (rc == 0) {
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399 LinuxAttachListener::write_fully(this->socket(), (char*) st->base(), st->size());
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400 ::shutdown(this->socket(), 2);
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401 }
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402
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403 // done
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404 RESTARTABLE(::close(this->socket()), rc);
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405
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406 // were we externally suspended while we were waiting?
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407 thread->check_and_wait_while_suspended();
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408
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409 delete this;
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410 }
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411
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412
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413 // AttachListener functions
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414
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415 AttachOperation* AttachListener::dequeue() {
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416 JavaThread* thread = JavaThread::current();
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417 ThreadBlockInVM tbivm(thread);
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418
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419 thread->set_suspend_equivalent();
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420 // cleared by handle_special_suspend_equivalent_condition() or
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421 // java_suspend_self() via check_and_wait_while_suspended()
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422
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423 AttachOperation* op = LinuxAttachListener::dequeue();
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424
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425 // were we externally suspended while we were waiting?
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426 thread->check_and_wait_while_suspended();
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427
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428 return op;
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429 }
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430
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431 int AttachListener::pd_init() {
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432 JavaThread* thread = JavaThread::current();
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433 ThreadBlockInVM tbivm(thread);
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434
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435 thread->set_suspend_equivalent();
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436 // cleared by handle_special_suspend_equivalent_condition() or
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437 // java_suspend_self() via check_and_wait_while_suspended()
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438
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439 int ret_code = LinuxAttachListener::init();
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440
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441 // were we externally suspended while we were waiting?
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442 thread->check_and_wait_while_suspended();
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443
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444 return ret_code;
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445 }
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446
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447 // Attach Listener is started lazily except in the case when
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448 // +ReduseSignalUsage is used
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449 bool AttachListener::init_at_startup() {
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450 if (ReduceSignalUsage) {
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451 return true;
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452 } else {
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453 return false;
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454 }
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455 }
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456
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457 // If the file .attach_pid<pid> exists in the working directory
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458 // or /tmp then this is the trigger to start the attach mechanism
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459 bool AttachListener::is_init_trigger() {
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460 if (init_at_startup() || is_initialized()) {
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461 return false; // initialized at startup or already initialized
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462 }
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463 char fn[32];
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464 sprintf(fn, ".attach_pid%d", os::current_process_id());
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465 int ret;
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466 struct stat64 st;
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467 RESTARTABLE(::stat64(fn, &st), ret);
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468 if (ret == -1) {
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469 sprintf(fn, "/tmp/.attach_pid%d", os::current_process_id());
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470 RESTARTABLE(::stat64(fn, &st), ret);
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471 }
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472 if (ret == 0) {
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473 // simple check to avoid starting the attach mechanism when
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474 // a bogus user creates the file
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475 if (st.st_uid == geteuid()) {
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476 init();
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477 return true;
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478 }
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479 }
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480 return false;
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481 }
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482
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483 // if VM aborts then remove listener
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484 void AttachListener::abort() {
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485 listener_cleanup();
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486 }
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487
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488 void AttachListener::pd_data_dump() {
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489 os::signal_notify(SIGQUIT);
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490 }
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491
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492 AttachOperationFunctionInfo* AttachListener::pd_find_operation(const char* n) {
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493 return NULL;
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494 }
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495
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496 jint AttachListener::pd_set_flag(AttachOperation* op, outputStream* out) {
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497 out->print_cr("flag '%s' cannot be changed", op->arg(0));
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498 return JNI_ERR;
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499 }
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500
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501 void AttachListener::pd_detachall() {
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502 // do nothing for now
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503 }
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